File Formats for GIS Data
Vector Data:
- Shapefile
- Developed by ESRI for ArcView GIS
- Specification is readily available; supported by other software
- Does not support the storage of topological information
- Can only store one feature class
- It is a collection of 3 or more files:
- Required files:
- Main file: .shp
- This is the primary file that stores feature geometry.
- "It's a direct access, variable-record-length file in which each record describes a shape with a list of its vertices." (ESRI)
- Stores integer and double-precision numbers (ESRI)
- Index file: .shx
- Stores the index of the feature geometry.
- "Each record contains the offset of the corresponding main file record from the beginning of the main file." (ESRI)
- Dbase table: .dbf
- Stores the attribute data for features contained in .shp, with one record per feature.
- There is a one-to-one relationship between geometry and attributes, which is based on record number. Attribute records in the dBASE file must be in the same order as records in the main file.
- It is a mix of binary and ASCII data. Header contains binary data. The records are all in ASCII. (XBase)
- Optional files:
- Sources:
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AprilWebster - 12 Mar 2007
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Topic revision: r3 - 2007-03-26 - AprilWebster